The present invention relates to a godet used for advancing, guiding, and heating an advancing synthetic filament yarn during the processing of the yarn. A godet of this general type is known, for example, from German Utility Model No. 1694542.
When heat treating an advancing yarn by means of a godet that advances the yarn, it is necessary that the rotating godet casing have over its entire surface a uniform surface temperature. To this end, the godet is conventionally heated by a radiation heater that is arranged in the interior of the godet and aligned substantially parallel to the godet casing.
Since the yarn loops several times about the godet casing along an axial contact length, it is also necessary that the godet casing have a substantially constant surface temperature along the entire contact length. However, in this connection, major heat losses are usually incurred in the end regions of the godet by thermal conduction or by circulating cooling air.
DE 195 32 036 C1 addresses this problem, and proposes that an adjustable cover be arranged between the radiation heater and the godet casing, so that in the godet casing heating zones are formed, which are more or less intensely heated depending on the adjustment of the cover. However, this arrangement has the considerable disadvantage of poor efficiency, since the cover shields from the godet casing the heat that is permanently generated by the radiation heater.
Likewise, the arrangement disclosed in U.S. Pat. No. 4,880,961 concerns a mode of operation of the radiation heater with poor efficiency, since the heat generated by the radiation heater must penetrate a wall of different thicknesses, so as to heat the godet casing.
Accordingly, it is an object of the invention to provide a godet of the above described type wherein the godet casing is heated by means of radiation heat such that the contact length of the godet has a substantially constant surface temperature.
A further object of the invention is to provide a godet, in which the energy generated by the heater results in heating the godet casing without significant losses.